In recent years, a substantial amount of research has been conducted for an illumination device which emits, as illuminating light, fluorescence that is generated by irradiating a light emitting section containing a fluorescent material with excitation light emitted by an excitation light source (i.e. semiconductor light emitting element) such as an LED (Light Emitting Diode) or an LD (Laser Diode).
Also, in order to achieve a reduction in energy consumption in the light of environmental issues, there has been a demand for an increase in efficiency in use of light emitted from a light emitting element (such as an LED, an LD, a fluorescent material light-emitting section etc.) of an illumination device (hereinafter, referred to simply as light utilization efficiency).
A light source device disclosed in Patent Literature 1 uses, as illuminating light, visible light generated, as spontaneously-emitted light, by irradiating a fluorescent material with a laser beam. According to the light source device, there is provided, in front of the fluorescent material facing a direction in which fluorescence is to be emitted, an ultraviolet rays reflecting mirror serving as a laser beams reflecting mirror. This causes a laser beam, which has not been absorbed by the fluorescent material, to be reflected from the ultraviolet rays reflecting mirror so that the fluorescent material is irradiated again with reflected laser beam. This prevents, from being emitted outside, a laser beam which has not been converted by the fluorescent material into visible light. A laser beam, which (i) was reflected by the ultraviolet rays reflecting mirror and (ii) re-entered the fluorescent material, is converted by the fluorescent material into spontaneously-emitted light. This allows light utilization efficiency to be enhanced.
Furthermore, Patent Literatures 2 and 3 each disclose a light source including a lens that converges, onto a fluorescent material, light emitted from a semiconductor light emitting element.